Allow surface rows and cols be in ascending or descending XZ order

This allows adding rows that have smaller Z-value than the
previously added row instead of being forced to insert rows
into the beginning of the data array in these cases.

Task-number: QTRD-2428
Change-Id: I4dc6c5a48a55ca494a2372f917aa7447f61f336e
Reviewed-by: Tomi Korpipää <tomi.korpipaa@digia.com>

2 files changed, 66 insertions, 36 deletions

diff --git a/src/datavisualization/data/qsurfacedataproxy.cpp b/src/datavisualization/data/qsurfacedataproxy.cpp
index 2e66bb5b..f8f2c900 100644
--- a/src/datavisualization/data/qsurfacedataproxy.cpp
+++ b/src/datavisualization/data/qsurfacedataproxy.cpp
@@ -28,8 +28,8 @@ QT_BEGIN_NAMESPACE_DATAVISUALIZATION
  * \brief Base proxy class for Q3DSurface.
  * \since Qt Data Visualization 1.0
  *
- * QSurfaceDataProxy takes care of surface related data handling. The QSurfaceDataProxy handles the data
- * in rows and for this it provides two auxiliary typedefs. QSurfaceDataArray is a QList for
+ * QSurfaceDataProxy takes care of surface related data handling. The QSurfaceDataProxy handles the
+ * data in rows and for this it provides two auxiliary typedefs. QSurfaceDataArray is a QList for
  * controlling the rows. For rows there is a QVector QSurfaceDataRow which contains QSurfaceDataItem
  * objects. See Q3DSurface documentation and basic sample code there how to feed the data for the
  * QSurfaceDataProxy.
@@ -41,17 +41,18 @@ QT_BEGIN_NAMESPACE_DATAVISUALIZATION
  * If you use QSurfaceDataRow pointers to directly modify data after adding the array to the proxy,
  * you must also emit proper signal to make the graph update.
  *
- * To make a sensible surface, the X-value of each successive item in the same row must be greater than the
- * previous item in that row, and the the Z-value of each successive item in a column  must be greater than
- * the previous item in that column.
+ * To make a sensible surface, the X-value of each successive item in all rows must be
+ * either ascending or descending throughout the row.
+ * Similarly, the Z-value of each successive item in all columns must be either ascending or
+ * descending throughout the column.
  *
- * \note In the initial release, only surfaces with straight rows and columns are fully supported. Any row
- * with items that do not have the exact same Z-value or any columns with items that do not have the exact
- * same X-value may get clipped incorrectly if the whole surface doesn't fit to the visible X or Z axis
- * ranges.
+ * \note Currently only surfaces with straight rows and columns are fully supported. Any row
+ * with items that do not have the exact same Z-value or any column with items that do not have
+ * the exact same X-value may get clipped incorrectly if the whole surface doesn't completely fit
+ * in the visible X or Z axis ranges.
  *
  * \note Surfaces with less than two rows or columns are not considered valid surfaces and will
- * not get rendered.
+ * not be rendered.
  *
  * \sa {Qt Data Visualization Data Handling}
  */
diff --git a/src/datavisualization/engine/surface3drenderer.cpp b/src/datavisualization/engine/surface3drenderer.cpp
index 56219104..d3898476 100644
--- a/src/datavisualization/engine/surface3drenderer.cpp
+++ b/src/datavisualization/engine/surface3drenderer.cpp
@@ -581,71 +581,100 @@ QRect Surface3DRenderer::calculateSampleRect(const QSurfaceDataArray &array)
 {
     QRect sampleSpace;
 
-    int rowCount = array.size();
-    int columnCount = array.at(0)->size();
-
-    int i;
-    bool found;
-    float axisMinX = m_axisCacheX.min();
-    float axisMaxX = m_axisCacheX.max();
-    float axisMinZ = m_axisCacheZ.min();
-    float axisMaxZ = m_axisCacheZ.max();
-
+    const int rowCount = array.size();
+    const int columnCount = array.at(0)->size();
+
+    const float axisMinX = m_axisCacheX.min();
+    const float axisMaxX = m_axisCacheX.max();
+    const float axisMinZ = m_axisCacheZ.min();
+    const float axisMaxZ = m_axisCacheZ.max();
+
+    // We assume data is ordered sequentially in rows for X-value and in columns for Z-value.
+    // Determine if data is ascending or descending in each case.
+    const bool ascendingX = array.at(0)->at(0).x() < array.at(0)->at(columnCount - 1).x();
+    const bool ascendingZ = array.at(0)->at(0).z() < array.at(rowCount - 1)->at(0).z();
+
+    const int minCol = ascendingX ? 0 : columnCount - 1;
+    const int maxCol = ascendingX ? columnCount - 1 : 0;
+    const int colStep = ascendingX ? 1 : -1;
+    const int minRow = ascendingZ ? 0 : rowCount - 1;
+    const int maxRow = ascendingZ ? rowCount - 1 : 0;
+    const int rowStep = ascendingZ ? 1 : -1;
+
+    bool found = false;
+    int idx = 0;
+    int i = 0;
     // m_minVisibleColumnValue
-    for (i = 0, found = false; i < columnCount; i++) {
-        if (array.at(0)->at(i).x() >= axisMinX) {
+    for (i = 0, idx = minCol, found = false; i < columnCount; i++) {
+        if (array.at(0)->at(idx).x() >= axisMinX) {
             found = true;
             break;
         }
+        idx += colStep;
     }
     if (found) {
-        m_minVisibleColumnValue = array.at(0)->at(i).x();
-        sampleSpace.setLeft(i);
+        m_minVisibleColumnValue = array.at(0)->at(idx).x();
+        if (ascendingX)
+            sampleSpace.setLeft(idx);
+        else
+            sampleSpace.setRight(idx);
     } else {
         sampleSpace.setWidth(-1); // to indicate nothing needs to be shown
         return sampleSpace;
     }
 
     // m_maxVisibleColumnValue
-    for (i = columnCount - 1, found = false; i >= 0; i--) {
-        if (array.at(0)->at(i).x() <= axisMaxX) {
+    for (i = 0, idx = maxCol, found = false; i < columnCount; i++) {
+        if (array.at(0)->at(idx).x() <= axisMaxX) {
             found = true;
             break;
         }
+        idx -= colStep;
     }
     if (found) {
-        m_maxVisibleColumnValue = array.at(0)->at(i).x();
-        sampleSpace.setRight(i);
+        m_maxVisibleColumnValue = array.at(0)->at(idx).x();
+        if (ascendingX)
+            sampleSpace.setRight(idx);
+        else
+            sampleSpace.setLeft(idx);
     } else {
         sampleSpace.setWidth(-1); // to indicate nothing needs to be shown
         return sampleSpace;
     }
 
     // m_minVisibleRowValue
-    for (i = 0, found = false; i < rowCount; i++) {
-        if (array.at(i)->at(0).z() >= axisMinZ) {
+    for (i = 0, idx = minRow, found = false; i < rowCount; i++) {
+        if (array.at(idx)->at(0).z() >= axisMinZ) {
             found = true;
             break;
         }
+        idx += rowStep;
     }
     if (found) {
-        m_minVisibleRowValue = array.at(i)->at(0).z();
-        sampleSpace.setTop(i);
+        m_minVisibleRowValue = array.at(idx)->at(0).z();
+        if (ascendingZ)
+            sampleSpace.setTop(idx);
+        else
+            sampleSpace.setBottom(idx);
     } else {
         sampleSpace.setWidth(-1); // to indicate nothing needs to be shown
         return sampleSpace;
     }
 
     // m_maxVisibleRowValue
-    for (i = rowCount - 1, found = false; i >= 0; i--) {
-        if (array.at(i)->at(0).z() <= axisMaxZ) {
+    for (i = 0, idx = maxRow, found = false; i < rowCount; i++) {
+        if (array.at(idx)->at(0).z() <= axisMaxZ) {
             found = true;
             break;
         }
+        idx -= rowStep;
     }
     if (found) {
-        m_maxVisibleRowValue = array.at(i)->at(0).z();
-        sampleSpace.setBottom(i);
+        m_maxVisibleRowValue = array.at(idx)->at(0).z();
+        if (ascendingZ)
+            sampleSpace.setBottom(idx);
+        else
+            sampleSpace.setTop(idx);
     } else {
         sampleSpace.setWidth(-1); // to indicate nothing needs to be shown
         return sampleSpace;